I believe that in a Code Corner back in the '05 era, John Wiles had said
that MC cable was OK to use, then in a later Code Corner he says that it
isn't; I thought it was because part of the reason for a metal raceway
is physical protection, and EMT/FMC would be sturdier than MC. But then
I looked at the 2011 Code, which (as it currently stands) will allow MC:
(E) Direct-Current Photovoltaic Source and Output Circuits Inside a
Building. Where dc photovoltaic source or output circuits from a
building-integrated or other photovoltaic system are run inside a
building or structure, they shall be contained in metal raceways, Type
MC metal clad cable that complies with 250.118(10), or metal enclosures,
from the point of penetration of the surface of the building or
structure to the first readily accessible disconnecting means. The
disconnecting means shall comply with 690.14(A), (B), and (D). [ROP 4-228]
The new 690.31(E) is about ten times longer than the '08 edition, now
requiring the conduit to be >10" below the surface of the roof (to avoid
firefighting equipment venting the roof) and labeling along that conduit
too:
http://www.solarabcs.com/index.php?option=com_docman&task=doc_download&gid=248&&Itemid=72
And to save you a lookup:
250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit
conductors shall be one or more or a combination of the following:
...
(10) Type MC cable where listed and identified for grounding in
accordance with the following:
a. The combined metallic sheath and grounding conductor of interlocked
metal tape–type MC cable
b. The metallic sheath or the combined metallic sheath and grounding
conductors of the smooth or corrugated tube-type MC cable
-------- Original Message --------
Subject: Re: [RE-wrenches] 690.32(E) + MC?
From: R Ray Walters <[email protected]>
To: RE-wrenches <[email protected]>
Date: 2009/12/5 03:28
I think the issue here is 690.32 deals just with 'fittings and
connectors', not the actual wire or cable. I believe you meant to
reference 690.31 which says 'all raceway and cable wiring methods
included in this code....shall be permitted'. But you still have to
comply with 690.31E which says it needs to be in 'metal raceways or
metal enclosures' once it enters the building up to the first readily
accessible disconnect. Looking at article 100, the definition of
raceway does include flexible metal conduit, so it seems you could
use metal flex conduit and pull wire, but I know many inspectors
still won't allow it. Reading up in articles 320 and 330 for AC and
MC cables, MC doesn't say it's conduit, so it would be out, but AC
says its enclosed in a 'flexible metallic enclosure'. So now the
question is: Is metallic the same as metal? (Oh Boy are we splitting
semantic hairs now.......). Bill or William are the ones to clarify
better than I on all of this, though. They've been involved in the
actual writing of the code. IMHO, it seems yet another point to be
clarified in future additions of the code. Meanwhile to be safe, most
of us are just running EMT once we penetrate the building. (which
opens yet another question: when have you penetrated the building?
above or below the roof flashing?)
I think I've caused enough trouble for now,
R. Walters [email protected] Solar Engineer
On Dec 4, 2009, at 7:47 PM, Darryl Thayer wrote:
I have always read metal conduit, The reason being the solar is
unfused source circuits, and there is no way for overcurrent
protective devices to open. Therefore, the conductors must be
protected from starting a fire under conditions of continuous
overcurrent. darryl
--- On Fri, 12/4/09, [email protected]
<[email protected]> wrote:
From: [email protected] <[email protected]> Subject:
[RE-wrenches] 690.32(E) + MC? To: "RE-wrenches"
<[email protected]> Date: Friday, December 4,
2009, 5:18 PM I did a project a while ago for a supplier /
Installing out fit (who has their in house engineering types),
who told me that either MC or maybe AC cable did comply with
690.32E. today I'm being told that's not the case, and I can't
seem to put my finger on it ... any pointers? thanks db
Dan Brown President Foxfire Energy Corp. Renewable Energy Systems
(802)-483-2564 www.Foxfire-Energy.com NABCEP #092907-44
-----Inline Attachment Follows-----
_______________________________________________ List sponsored by
Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette: www.re-wrenches.org/etiquette.htm
Check out participant bios: www.members.re-wrenches.org
_______________________________________________ List sponsored by
Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette: www.re-wrenches.org/etiquette.htm
Check out participant bios: www.members.re-wrenches.org
_______________________________________________ List sponsored by
Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette: www.re-wrenches.org/etiquette.htm
Check out participant bios: www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
